1. Field of the Invention
This invention relates broadly to the field of thrust control devices for use with jet engines. More particularly, this invention relates to those thrust control devices intended to spoil and/or deflect the hot core exhaust flow. Although this invention finds particular utility in the field of turbofan engines, it is clear that the advantages of the invention are equally well manifest in other engine applications wherever low cost, reliable thrust spoiling is required. The invention is useful not only upon landing, but also during taxiing where relatively high engine speeds may be required to keep the engine lit.
2. Background of the Invention
Various arrangements for spoiling and/or deflecting the thrust of a jet engine are known. These devices, frequently termed thrust reversers, are either mounted within the engine itself or are mounted on some portion of the aircraft frame adjacent the engine. Because of their constant exposure to the high temperature environment of the engine, devices of the former type require high cost, high temperature-tolerant materials. As a result, maintenance costs are high. On turbofan installations where separate, fan-only reversers are available, the core flow reversers are frequently not used. Since forward core thrust is subtracted from fan-only reverse thrust, only about 21-24% total retarding force is generated using a maximum efficiency fan-only reverser delivering 45% or more reverse thrust. Use of maximum efficiency fan-only reversers may not be practical since such devices are subject to reingestion of flow turbulence at aircraft speeds below about 60-70 knots. In this situation total stopping distance may actually be reduced by providing a less efficient fan-only reverser that may be used down to about 30 knots without suffering reingestion difficulties. While this may be operationally adequate, undesirable brake and tire wear and associated maintenance and replacement costs result. Obviously, if a greater stopping force could be generated by the engines, e.g., by using a 30% fan-only reverser along with a core flow reverser, the brake use necessary to stop the aircraft would be reduced. Since most core flow reversers are mounted within the engine, they cannot be easily removed even if they are not being used, which adds unnecessary dead weight to the aircraft. Devices of the latter type, i.e., a spoiler or deflector mounted downstream of the nozzle exit plane, have apparently found their greatest utility in the field of V/STOL aircraft. These devices are generally complex arrangements of deflecting vanes mounted in a retractable frame to properly orient the thrust for optimum short take-off and landing performance. As a result, they are frequently quite bulky and require relatively complex operating mechanisms for the vanes, which renders compact stowage difficult. Additionally, apparently none of these devices are intended to affect only the hot core exhaust flow.
It is, accordingly, an object of the present invention to provide a simple, lightweight and easily installed thrust control device which overcomes these and other limitations and disadvantages of the prior art.
It is another object to provide a thrust control device that may be easily adapted for a variety of engine installations.
It is a further object of the invention to provide a thrust control device that is actuated in a novel manner to permit compact stowage when not in use.
It is yet another object of the invention to provide a thrust control device that affects only the hot exhaust core flow.
It is another object to provide a thrust control device that may be easily modified and adapted to provide the optimum amount of thrust deflection and spoiling for a particular installation.
It is still another object to provide a thrust controller designed and mounted to cool the mounting hardware during thrust spoiling.